Generally, many modern high bypass turbofan engines used in commercial passenger and military transport aircraft use fan rotor speed settings to guarantee thrust during critical flight segments such as takeoff and climb to ensure safety and proper flight characteristics. Many factors are used to set thrust and the corresponding required engine fan speed. Variables that affect the settings include possible combinations of the following items: aircraft weight, ambient temperature, altitude, humidity, wind speed and other airport operational factors. To guarantee the required thrust, engine manufacturers must account for uncertainty in items such as sensor measurement biases, transient overshoots and engine deterioration. Consideration of the listed variables results in a stacked list of uncertainties. The stack-up applies to new engines and engines near the end of their hot section life. Because of the thrust setting approach, new engines often produce more thrust than required during takeoff and climb mission segments. As a result, newer engines use up turbine life by operating at higher than required temperatures and speeds.